TUN-7134: Acquire token for cloudflared tail

cloudflared tail will now fetch the management token from by making
a request to the Cloudflare API using the cert.pem (acquired from
cloudflared login).

Refactored some of the credentials code into it's own package as
to allow for easier use between subcommands outside of
`cloudflared tunnel`.

cmd/cloudflared/tunnel/subcommand_context.go

@@ -13,9 +13,9 @@ import (
 	"github.com/rs/zerolog"
 	"github.com/urfave/cli/v2"
 
-	"github.com/cloudflare/cloudflared/certutil"
 	"github.com/cloudflare/cloudflared/cfapi"
 	"github.com/cloudflare/cloudflared/connection"
+	"github.com/cloudflare/cloudflared/credentials"
 	"github.com/cloudflare/cloudflared/logger"
 )
 
@@ -37,7 +37,7 @@ type subcommandContext struct {
 
 	// These fields should be accessed using their respective Getter
 	tunnelstoreClient cfapi.Client
-	userCredential    *userCredential
+	userCredential    *credentials.User
 }
 
 func newSubcommandContext(c *cli.Context) (*subcommandContext, error) {
@@ -56,65 +56,28 @@ func (sc *subcommandContext) credentialFinder(tunnelID uuid.UUID) CredFinder {
 	return newSearchByID(tunnelID, sc.c, sc.log, sc.fs)
 }
 
-type userCredential struct {
-	cert     *certutil.OriginCert
-	certPath string
-}
-
 func (sc *subcommandContext) client() (cfapi.Client, error) {
 	if sc.tunnelstoreClient != nil {
 		return sc.tunnelstoreClient, nil
 	}
-	credential, err := sc.credential()
+	cred, err := sc.credential()
 	if err != nil {
 		return nil, err
 	}
-	userAgent := fmt.Sprintf("cloudflared/%s", buildInfo.Version())
-	client, err := cfapi.NewRESTClient(
-		sc.c.String("api-url"),
-		credential.cert.AccountID,
-		credential.cert.ZoneID,
-		credential.cert.APIToken,
-		userAgent,
-		sc.log,
-	)
-
+	sc.tunnelstoreClient, err = cred.Client(sc.c.String("api-url"), buildInfo.UserAgent(), sc.log)
 	if err != nil {
 		return nil, err
 	}
-	sc.tunnelstoreClient = client
-	return client, nil
+	return sc.tunnelstoreClient, nil
 }
 
-func (sc *subcommandContext) credential() (*userCredential, error) {
+func (sc *subcommandContext) credential() (*credentials.User, error) {
 	if sc.userCredential == nil {
-		originCertPath := sc.c.String("origincert")
-		originCertLog := sc.log.With().
-			Str(LogFieldOriginCertPath, originCertPath).
-			Logger()
-
-		originCertPath, err := findOriginCert(originCertPath, &originCertLog)
+		uc, err := credentials.Read(sc.c.String(credentials.OriginCertFlag), sc.log)
 		if err != nil {
-			return nil, errors.Wrap(err, "Error locating origin cert")
-		}
-		blocks, err := readOriginCert(originCertPath)
-		if err != nil {
-			return nil, errors.Wrapf(err, "Can't read origin cert from %s", originCertPath)
-		}
-
-		cert, err := certutil.DecodeOriginCert(blocks)
-		if err != nil {
-			return nil, errors.Wrap(err, "Error decoding origin cert")
-		}
-
-		if cert.AccountID == "" {
-			return nil, errors.Errorf(`Origin certificate needs to be refreshed before creating new tunnels.\nDelete %s and run "cloudflared login" to obtain a new cert.`, originCertPath)
-		}
-
-		sc.userCredential = &userCredential{
-			cert:     cert,
-			certPath: originCertPath,
+			return nil, err
 		}
+		sc.userCredential = uc
 	}
 	return sc.userCredential, nil
 }
@@ -175,13 +138,13 @@ func (sc *subcommandContext) create(name string, credentialsFilePath string, sec
 		return nil, err
 	}
 	tunnelCredentials := connection.Credentials{
-		AccountTag:   credential.cert.AccountID,
+		AccountTag:   credential.AccountID(),
 		TunnelSecret: tunnelSecret,
 		TunnelID:     tunnel.ID,
 	}
 	usedCertPath := false
 	if credentialsFilePath == "" {
-		originCertDir := filepath.Dir(credential.certPath)
+		originCertDir := filepath.Dir(credential.CertPath())
 		credentialsFilePath, err = tunnelFilePath(tunnelCredentials.TunnelID, originCertDir)
 		if err != nil {
 			return nil, err